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AudioFlinger: refine mixer sleep time logic

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When an AudioTrack is in underrun state, the AudioFlinger mixer will
sleep for a short period of time to give the app a chance to fill the
AudioTrack buffer. If the AudioTrack is still not ready during next mixing round,
the mixer will proceed with other tracks.

If an application keeps a steady underrun condition, the AudioFlinger mixer will
alternate between ready and not ready states. In the longer term this will cause the
audio HAL to underrun.
There is a mechanism to reduce the sleep period if the mixer is not ready several times in a
row but this mechanism is defeated by the alternating ready/not ready conditions.

The fix consists in only increasing sleep time if the mixer is ready for at least two
consecutive times.

Issue 5904527.

Change-Id: Id0139bca9be8c4e425ec6d428515c4d8f718e8c9
This commit is contained in:
Eric Laurent
2012-01-23 18:56:59 -08:00
parent 0b08965558
commit 0609231f4f
1 changed files with 6 additions and 3 deletions
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9
services/audioflinger/AudioFlinger.cpp
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@@ -1973,11 +1973,14 @@ bool AudioFlinger::MixerThread::threadLoop()
if (LIKELY(mixerStatus == MIXER_TRACKS_READY)) {
// mix buffers...
mAudioMixer->process();
sleepTime = 0;
// increase sleep time progressively when application underrun condition clears
if (sleepTimeShift > 0) {
// increase sleep time progressively when application underrun condition clears.
// Only increase sleep time if the mixer is ready for two consecutive times to avoid
// that a steady state of alternating ready/not ready conditions keeps the sleep time
// such that we would underrun the audio HAL.
if ((sleepTime == 0) && (sleepTimeShift > 0)) {
sleepTimeShift--;
}
sleepTime = 0;
standbyTime = systemTime() + kStandbyTimeInNsecs;
//TODO: delay standby when effects have a tail
} else {